1. Field of the Invention
The present invention relates a method of bonding veneer sheets and an apparatus therefor to manufacture sheet material, such as plywood, LVL, and LVB, and more particularly to a veneer bonding method and an apparatus therefor with a veneer lathe, or the like, before the veneer sheets cut off from a log are dried, that is, under a condition that the veneer sheets are so-called unseasoned (hereinafter referred to as "unseasoned veneers").
2. Description of the Related Art
Conventionally, when unseasoned veneers are bonded to each other, for example, after powdery bonding agent is adhered to bonding faces of the unseasoned veneers, the bonding faces are adjusted to each other, and then the bonding faces are forcibly dried and bonded to each other through concentrated heating at bonded portions of the unseasoned veneers from their surfaces, or after the bonding faces of the unseasoned veneers are heated and dried in advance, and then bonding agent is applied to adjust the bonding faces to each other, the bonding faces are pressurized under heat so as to be bonded to each other, or thermosetting bonding agent is applied to the bonding faces of the unseasoned veneers and microwave is applied to the bonding surfaces while the bonding faces are contacted to each other to bond them to each other.
In the conventional unseasoned veneer bonding method described above, when powdery bonding agent is applied to the bonding faces of the unseasoned veneers and then the bonding faces are heated to bond the faces to each other, if moisture content of the unseasoned veneers to be bonded is low, the powdery bonding agent is not susceptible to be adhered to the bonding faces, so that it is required to select unseasoned veneers with more or equal to approximately 70% of moisture content.
Further, when the bonding face portions of the unseasoned veneers are heated and dried in advance before applying bonding agent to bond the unseasoned veneers to each other, a heating and drying apparatus for the heating and drying is separately necessary, so that overall apparatus becomes large for the heating and drying apparatus.
Further, when the unseasoned veneers are bonded to each other through microwave, heating velocity by the microwave is determined by output of the apparatus, kinds of tree from which the unseasoned veneer is manufactured, moisture content or direction of fibers of the unseasoned veneers, water content of the bonding agent, or amount of the bonding agent applied, and instant treatment with large output causes rapid increase of the temperature of the inside of the unseasoned veneers to excessively increase vaporization of the water, which may cause a fear of crack on the unseasoned veneers.